Field of the Invention
The present invention relates to a light source unit having a wavelength conversion member and a projector including this light source unit.
Description of the Related Art
In these days, data projectors are used on many occasions as an image projection system which projects an image of a screen of a personal computer or a video image, as well as images based on image data which is stored on a memory card on to a screen. In these data projectors, light emitted from a light source is caused to converge to a micromirror display device called a DMD (Digital Micromirror Device) or a liquid crystal panel so that a full-color image is displayed onto a screen.
In addition, the application of such projectors is expanding widely from commercial presentation to domestic use as video equipment including personal computers, DVD players and the like has been used generally. Conventionally, the mainstream of these projectors has been those which utilize a high-intensity discharge lamp as a light source. In recent years, however, there have been made many developments and proposals on light source units which use, as a light source, a plurality of semiconductor light emitting elements such as laser diodes and which include a plurality of optical parts such as lenses, mirrors and the like in association with the use of such semiconductor light emitting elements.
For example, a light source unit of a projector which is disclosed in Japanese Unexamined Patent Publication No. 2011-13320 (JP-A-2011-13320) has a blue laser oscillator as a light source of light in the blue wavelength range, a red light emitting diode as alight source of light in the red wavelength range and a luminescent wheel device which includes a luminescent wheel having laid out thereon a luminescent material layer which emits light in the green wavelength range using, as excitation light, light emitted from a blue laser oscillator which is a light source of light in the blue wavelength range. The luminescent wheel includes a diffuse transmission area which transmits light emitted from the blue laser oscillator while diffusing the light. The light in the blue wavelength range which passes through the diffuse transmission area is shone on to the display device as a light source together with light in the red wavelength range and light in the green wavelength range, and projected light from the display device is projected on to a screen.
The blue laser oscillator (the blue laser diode) used in the projector disclosed in JP-A-2011-13320 is configured to be suitable for the projector as it is made to exhibit a high light output and to cause light in the green wavelength range to be emitted efficiently. It is understood that the wavelength of light emitted from this blue laser oscillator is close to about 450 nm. In case light whose wavelength is close to about 450 nm is projected on to a screen as a light source, projected light which should be blue looks slightly purplish, leading from time to time a problem that the color tone of a projected image becomes unnatural.
Consequently, an object of the invention is to provide a light source unit which can project an image with a proper color tone on to a screen when a blue laser diode is used as a light source and a projector which uses this light source unit.